FRANKFORT, KY. -- Sen. Albert Gore Jr. (D-Tenn.) was asked at a news conference here Tuesday why he is now emphasizing economic issues rather than defense and presenting himself as a populist rather than a hawk in his presidential campaign.

Gore has based his campaign hopes on doing well in the predominantly southern "Super Tuesday" primaries next week by presenting himself as a moderately conservative, tough-on-communism southerner. He responded that he was the one who had raised the defense issue at the candidates' debate in Williamsburg, Va., the previous night.

A major premise of Gore's campaign is that, only by nominating a candidate who can carry the South, can the Democrats regain the White House. He has spent much of the campaign contending that he is the person most likely to do this because he best understands that the United States must meet its global responsibilities from a position of military strength.

In the last week or two, however, Gore has concentrated on economic and domestic issues. On both foreign and domestic issues, he has sounded very much like a traditional Democrat.

Gore contends that he is discussing the same issues that have engaged him in his 12 years in the House and Senate. But aides privately acknowledge that the new emphasis is in response to the effectiveness in the South of the message by Rep. Richard A. Gephardt (D-Mo.) of what they call "economic nationalism."

At a rally in Louisville, Gore reminded his audience that "we are the party in the tradition of Franklin Roosevelt, Harry Truman and John F. Kennedy."

At a hospital in Richmond, where he visited liver transplant patients, Gore sounded the Democrats' belief in active government by noting that "there are some problems people just can't solve on their own, so we must get together and solve them through government."

Gore defines his priorities as "economic growth and justice, jobs and making America competitive again."

He told a Louisville audience: "I'm running to bring the White House back to the grass roots, to put it on the side of working men and women. Republicans ask what's best for the country club set. We need a Democratic president who asks what's best for the man on the assembly line, the coal miner, the farmer and the woman behind the typewriter."

Although at 39 he is the youngest candidate of either party, he argues that this is offset by his 12 years in the House and Senate and notes that, if elected, he would be less than two years younger than President John F. Kennedy when he took office in 1961.

Gore contends that "sacrifice will be necessary" in solving economic and trade problems and that the country "must have a president who's willing to fight for the average working men and women as those sacrifices are allocated in this country."

He agrees that the federal budget deficit is a major problem but cites other priorities and says the attempt to reduce it must be done carefully.

"The challenge is not to suddenly balance the budget in one, two or three years but to reestablish confidence in our ability to cut spending and exercise some control over fiscal policy and our economic destiny," he says. "We can straighten out our economic problems by electing a president who personally knows every committee chairman and subcommittee chairman on both sides of Capitol Hill and can work in partnership with them."

To this end, he proposes partial means testing for some entitlement programs, which he does not specify, reducing farm subsidies by restricting them to family farms and reducing military spending through conventional and strategic arms-control agreements, procurement reforms and having Japan and the European allies shoulder more of the defense burden.

"We cannot indefinitely keep 350,000 troops in Europe, tens of thousands in Asia and 50,000 afloat," Gore says.

Gore would increase some spending, although he does not specify amounts: "A crash program on AIDS . . . and a renewed commitment to help give our children the best elementary and secondary schools on earth . . . . I will support the investments in research, training and education that are necessary to restore broad economic growth and make this nation competitive abroad."

Gore believes that "the rebuilding of America" can be accomplished without raising income taxes of middle-class workers, but, "as a last resort," says he would support such revenue sources as luxury taxes and maintaining the present corporate tax rate.

Gephardt's trade amendment, aimed at forcing fairness by trading partners who close their markets to U.S. goods through tariffs and duties, would be a "disaster" that "might trigger a new recession and launch a worldwide trade war," Gore says.

The solution is "to compete better by being better" through education and welfare reform that encourages the work ethic, he says. He also supports bilateral trade agreements because he thinks that current multilateral negotiations will take years to complete.

Gore finds it "outrageous" that a number of the Republican candidates oppose ratification of the Intermediate-Range Nuclear Forces missile agreement.

"The Russians will have to destroy more than four weapons for every one we do, we get on-site verification, which is a very important psychological and political breakthrough, and the British and French will have a virtual monopoly of intermediate-range weapons," he said.

"We were able to get this agreement because we deployed the missile in Europe. It's very important to go on to the next step, strategic arms control, and remove the obsession with the Strategic Defense Initiative."

Gore contends that the United States and Soviet Union now agree with his 1981 proposal that the ideal nuclear balance would be 500-600 single-warhead mobile missiles on both sides. He helped to obtain the ban on testing anti-satellite weapons in space and in limiting the number of MX missiles to 50.

Although he believes that protecting U.S.-flagged ships in the Persian Gulf began because of a "mistake," he supports it as being in "our best interest as a nation because it contains 70 percent of the free world's oil reserves" and is helping to prevent the region's balance of power from tipping to Iran and Islamic fundamentalism.

In Richmond this week, he voiced his support for a strong Navy, including deployment of 14 aircraft-carrier task forces and continued construction of two new carriers at Newport News, Va.

"It is disingenuous, dishonest and dangerous to ignore the fact that we live in a dangerous world," he says. "We cannot make a firm commitment to Israel and then cave in to pressure in this country to give up weapon system after weapon system."

A veteran of the Vietnam war, he thinks that it was "a serious mistake" that has led to other mistakes.

One is that, while "our nation must play a strong role in the world, . . . after the Vietnam war, a certain neo-isolationist impulse became a part of our national dialogue," he says. Another is that he fears that the Reagan administration is flirting with a similar situation in Nicaragua.

Gore supports the Arias peace plan for the area, has voted against military aid for the contras and supports nonlethal aid to "resettle them, either in Nicaragua or Florida." He contends that communism in the area is rooted in poverty as well as revolutionary politics.

"Leadership requires strength as well as wisdom," he says. "Franklin Roosevelt understood that . . . . Harry Truman understood it . . . . John F. Kennedy understood it . . . . That is the proud tradition of our party."